x Turn on thread page Beta
 You are Here: Home >< Physics

# Simple Harmonic Motion watch

1. Hi,

I have been studying this diagram:

There are some things that don't quite add up to me though. From the diagram you can see that the equation for the displacement x is:

x = Xcos(theta)

When the dot is to the far right theta is zero so x is equal to X and you get maximum displacement which I am fine with.

However, when the ball is above the center the displacement is zero but theta as it is given in the diagram doesn't make this work. When the ball is directly overhead there is no triangle you can draw so theta is zero again but this can't be the case as we know the displacement is zero at that point?
2. (Original post by Bibloski)
Hi,

I have been studying this diagram:

There are some things that don't quite add up to me though. From the diagram you can see that the equation for the displacement x is:

x = Xcos(theta)

When the dot is to the far right theta is zero so x is equal to X and you get maximum displacement which I am fine with.

However, when the ball is above the center the displacement is zero but theta as it is given in the diagram doesn't make this work. When the ball is directly overhead there is no triangle you can draw so theta is zero again but this can't be the case as we know the displacement is zero at that point?
When the point is directly overhead, is not 0. It is since this is the angle made by the line connecting P and the centre of the circle with the horizontal diameter.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: November 9, 2015
Today on TSR

### How much will your degree earn you?

Find out where yours ranks...

### I do my boyfriend's uni assignments

Poll
Useful resources

Can you help? Study help unanswered threadsStudy Help rules and posting guidelinesLaTex guide for writing equations on TSR

## Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE